108 EVENINGS AT THE MICKOSCOPE. 



wliicli exists in life, we may see the principle on "which 

 they are arranged, and much of the perfection with 

 which they are constructed. 



Here then is a system of pipes, — some large, some 

 small : the smaller branching forth from the larsre, 

 and themselves sending off yet smaller branches, which 

 in their turn divide and subdivide until the final rami- 

 fications are excessively attenuated. Besides these, we 

 see here and there ovate or barrel-shaped reservoirs, 

 having the same apj^earance and intimate structure as 

 the pipes, but of much larger calibre and connected 

 with them by a branch. 



This, I say, is the breathing system, or a large por- 

 tion of it. These pipes receive the air from without 

 through trap-doors, which we will examine presently, 

 and convey it to the most distant parts of the body. 

 In ourselves the air is inhaled into a great central reser- 

 voir, the lungs, and the blood dispersed through every 

 part is brought to this reservoir to be oxygenated. In 

 insects it is the blood that is collected into a great 

 central reservoir, and the air is distributed by a mi- 

 nutely divided system of vessels over the blood-reser- 

 voir. 



Tlie trachecB or air-pipes have a silvery white ap- 

 pearance by reflected light ; but if we use transmitted 

 light and put on a high power, we discern a wonderful 

 structure, which I will describe in the eloquent lan- 

 guage of Professor Eymer Jones, and you shall estimate 

 its truth as you examine the object : — 



" There is one elegant arrangement connected with 

 the breathing-tubes of an insect specially worthy of ad- 

 miration ; and perhaps in the whole range of animal 

 mechanics it %vould be difficult to point out an example 



